Welcome to HVAC-Talk.com, a non-DIY site and the ultimate Source for HVAC Information & Knowledge Sharing for the industry professional! Here you can join over 150,000 HVAC Professionals & enthusiasts from around the world discussing all things related to HVAC/R. You are currently viewing as a NON-REGISTERED guest which gives you limited access to view discussions

To gain full access to our forums you must register; for a free account. As a registered Guest you will be able to:

Participate in over 40 different forums and search/browse from nearly 3 million posts.

BLOWER WONT STOP

Rudd JGDG075AUER serCB5D302F38951719 After A/C hits its set point,Cond. shuts down blower keeps going. Remove 24v at board feeding stat,not that. Pull blower wire at "cool",nope! pulled blower wire at "heat" bingo! Got to thinking..,are hi limits etc. active in A/C call? in this unit they are. I had 24v.at all safty switches. They all tested Ok. BAD BOARD was my first and still diagnoses. Records show this is the 3rd board in as many years! I also checked voltage of unused blower wires while running in A/c mode.One to the heat spade was 115v,other 2 on park pins were 160v! ( is this normal,or do I have a blower that needs an exorcism?

Are the replacement boards aftermarket or oem? I had the same issue with an oem board and replaced it with a honeywell s920u. The honenywell has jumper wires and dip switch that need to set. What about polarity? Sounds like a stuck relay.

Rudd JGDG075AUER serCB5D302F38951719 After A/C hits its set point,Cond. shuts down blower keeps going. Remove 24v at board feeding stat,not that. Pull blower wire at "cool",nope! pulled blower wire at "heat" bingo! Got to thinking..,are hi limits etc. active in A/C call? in this unit they are. I had 24v.at all safty switches. They all tested Ok. BAD BOARD was my first and still diagnoses. Records show this is the 3rd board in as many years! I also checked voltage of unused blower wires while running in A/c mode.One to the heat spade was 115v,other 2 on park pins were 160v! ( is this normal,or do I have a blower that needs an exorcism?

That higher voltage on park terminals is due to the back EMF it is normal. The series safety circuit can be energized at all times, I have seen this with janitrols. Is their more than one safety circuit? Sometimes the liimit switch that sets beside the heat exchanger has its own circuit. It could be open that would keep the fan on constantly.

Rudd JGDG075AUER serCB5D302F38951719 After A/C hits its set point,Cond. shuts down blower keeps going. Remove 24v at board feeding stat,not that. Pull blower wire at "cool",nope! pulled blower wire at "heat" bingo! Got to thinking..,are hi limits etc. active in A/C call? in this unit they are. I had 24v.at all safty switches. They all tested Ok. BAD BOARD was my first and still diagnoses. Records show this is the 3rd board in as many years! I also checked voltage of unused blower wires while running in A/c mode.One to the heat spade was 115v,other 2 on park pins were 160v! ( is this normal,or do I have a blower that needs an exorcism?

Probably a stuck relay on the board, if you install another board, make sure since this is the 3rd board, some "blow and go" tech did not install the wrong hp motor were it's drawing to many amps for the relay on that board, seen this before.

__________________________________________________ _______________________Experience is a hard teacher because she gives the test first, the lesson afterwards". -Vernon Law-

Do you hear the fan relay click when the power to the furnace is first energized?
Another test you can do is take where the power comes into the board and ohm it to the motor output terminal that is staying energized. If it reads shorted the contacts are arced.